Extremely powerful insult usually directed towards someone when a more creative term than 'asshole' is needed. The implication is that the person is so amoral/stupid that they would fuck a gunt as opposed to a cunt. Reasons for this lack of proper copulation technique could range from indifference to desperation to a perverted sense of the need to humiliate oneself and sexual partner simultaneously.
Person A: Did you hear about Ronnie? He date-raped that retarded girl on Pearson Avenue.

Person B: Mikey's sister?!? That guntfucker! I'm gonna kill him.
by Joel Freeman May 28, 2008
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